Generally, a 3D image can be viewed by a passive way and an active way.
In the passive way for viewing a 3D image, the 3D image is projected in an overlapping manner on a screen by passing a left and right image through a polarization plate provided on a front and rear face of left and right projection lens, respectively. A viewer views the 3D image by using a polarization eye-glass that separates the left and right images for 3D viewing.
Here, the 3D image can be viewed where the 3D image is reflected originally on a screen in a state that a polarization degree of the left and right image of the 3D image is not damaged.
Meanwhile, in the active way for viewing a 3D image, the 3D image is divided into a left and right image and the left and right image are projected sequentially at predetermined time intervals on a screen. A viewer views the 3D image using a 3D eye-glass that has a left and right shutter which are opened and closed sequentially in a synchronizing manner with the left and right image, which is well known in the art.
However, since a light transmission rate of the 3D eye-glass is about 10%, the projected 3D image is typically to dark to see and thus it is impossible to view the 3D image unless a bright screen is used.
Accordingly, in the passive viewing of a 3D image, a screen for the 3D image has to have a reflection function to reflect the degree of the polarization and further the reflection rate of the polarization degree has to be good to view a 3D image.
Additionally, generally, for viewing a 2D image, a screen having a high reflection rate is required, since a brightness of a small projector such as a pico projector is too low.
However, it is well known that when the screen has a high reflection rate, the left and right viewing angles narrow which decreases the contrast resulting in a lower resolution. Therefore, the prior art screens are not able to be used for viewing a 2D image and a 3D image, but require separate screens in order to meet the above described demands depending on the image to be viewed on the screen.
As known in the prior art, Korea Utility Model registration No. 20-039904, which is entitled “both side non-reflection screen”, discloses a screen having both sides configured as a screen face. Even though both sides of the screen are configured as a screen face, the screen cannot have a multi-screen function and further is not configured to have a 3D image functionality.
Further, Korean Utility Model application No. 20-2004-0006510, which is entitled “multi-roll screen device”, discloses a single screen having two screen faces. Even though the single screen has two screen faces, one screen face is selected depending on demands, which doubles the volume, weight and cost and is not very practical. Additionally, this screen does not have 3D image functionality.
That is, the prior art fails to disclose a multi-sided screen that has both a 3D image functionality and a 2D image functionality.